Synthetic resin bottle-shaped container

ABSTRACT

A biaxially oriented blow-molded bottle-shaped container made of synthetic resin comprises a rectangular tubular body provided with a generally central circumferential groove having upper and lower sidewalls. The sidewalls are inclined at an oblique angle within a range of 21°-28° with respect to a vertical longitudinal axis of the container. The rectangular tubular body includes flat walls, each having a central recessed portion with a bottom wall comprising a shaped panel wall for compensating for deformation due to reduced pressure in the container and a shaped peripheral groove invertedly curved around the shaped panel wall. The shaped panel wall has ribs traversing the shaped panel wall parallel to each other, and a crest of each of the ribs has a larger radius of curvature than that of a root thereof. The rectangular tubular body has an upper end which is a regular polygon having twice as many corners as corner panels of a main portion of the body and a shoulder having a lower end portion connected to the upper end of the body. The lower end portion of the shoulder is in the form of a regular polygonal truncated pyramid shape.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a large bottle made of synthetic resin,and, more particularly, relates to the body wall structure of a largesquare bottle made of biaxially oriented blow molded polyethyleneterephthalate (hereinafter referred to as "PET"). The structure of thebottle including the body upper end to a shoulder and the wall structureof a ridge-line portion provides a significant influence upon theexternal appearance and configuration of the bottle by bending andconnecting two wall surface portions.

2. Description of Related Art

The biaxial oriented blow molded bottle of polyethylene terephthalateresin has excellent durability in various areas such as contentresistance, chemical resistance, weather resistance, shock resistanceand the like. Such a bottle also exhibits high mechanical strength,transparency, no pollution and gas barrier properties. Therefore, thistype of bottle has been used on a large scale for containing variouskinds of liquid.

However, the PET biaxial oriented blow molded large bottle does not havesufficient mechanical strength in its body, such as self configurationsustaining capability or buckling strength, since the body is a mainportion of the bottle and is thin in thickness. Particularly, a bottlehaving a square tubular body is poor in not only buckling strength butalso self configuration sustaining capability. Therefore, largedepressed deformations tend to occur in the body which are caused bynegative pressure generated within the bottle after a liquid iscontained and sealed therein.

In order to solve such problems in a square-shaped PET bottle, a centralcircumferential groove is provided at a substantial center of the bodyfor increasing buckling strength against depression force applied on thebottle from the outside and for increasing self configuration sustainingcapability of the body against external forces applied in thediametrical direction. At the central portion of a flat wall on thebody, divided into upper and lower portions by a central circumferentialgroove, a recessed portion is provided having a depression deformableshaped panel wall as a bottom wall for taking up negative pressuregenerated in the bottle by a certain depression deformation at theshaped panel wall to prevent any depression deformation from occurringin the body and to increase self configuration sustaining capability ofthe flat wall portion.

An increase in mechanical configuration sustaining capability byproviding a central circumferential groove and a recessed portion formedwith the shaped panel wall can be obtained by adding inclined groovesidewalls in the central circumferential groove and inclined groovesidewalls in the recessed portion as reinforcing rib wall pieces withrespect to the diametrical direction of the body.

Therefore, hitherto, in order to increase the function of inclinedgroove sidewalls and recess sidewalls of the central circumferentialgroove and the recessed portion as reinforcing rib wall pieces, obliqueangles of the groove sidewalls and recessed sidewalls with respect tothe central axis of the bottle have been set to large values.

The self configuration sustaining capability of the body of the bottle,particularly the vicinity of the central circumferential groove graspedby the hand is actively reinforced by setting the oblique angles of thegrooved sidewalls and recessed sidewalls at large values. However, whenmore than a certain pressure is applied to the body of the bottle at thetime of handling or at the time of casing and transporting bottles, thewall portion extending from the groove sidewalls and recessed sidewallsto the flat wall is sharply bent and/or depressedly deformed. Further,the deformed portion will not return to the original configuration evenif the pressure is removed, and the bent and/or depressed deformationthen becomes a permanent deformation which causes the commercial valueof the bottle to be lost.

The above-described conventional negative pressure accommodatingrecessed portion is constructed by forming the shaped panel wall with abottom wall having a shape which is easily deformable by negativepressure and absorbing negative pressure generated in the bottle by alarge depressed deformation at the central portion of the shaped panelwall. However, the negative pressure deformation of this shaped panelwall detracts from the external appearance of the bottle, which lowersthe aesthetic appearance and style of the bottle as a consumer good.

Moreover, the shaped panel wall occupying a large surface area at eachflat wall of the body is liable to deform. So, when grasping the bottleby the hand, the deformed panel wall where finger tips contact is easilydeformed, and the bottle becomes unstable to handle by hand.

Furthermore, as described above, the shaped panel wall occupies a largesurface area of each flat wall of the body, but the wall structure ofthis shaped panel wall is mainly a deformable flat structure. Thus, thebottle's external appearance becomes simple, which also makes theexternal appearance of the bottle dull.

As stated above, the concave and convex shaped panel wall is molded atthe flat wall portion of the body of a PET large square bottle, so thatit is extremely difficult to print a commercial name or a company nameor to stick and display a label. Hence, the commercial name or thecompany name is displayed with the aid of a shrunk label made of aheat-shrinkable sheet.

Since this shrunk label is originally a simple sheet, it is easy toprint patterns and to form the label onto a cylindrical body. It isfurther advantageous to strongly attach a label to the bottle by simplebut secure heat treatment. However, because of certain shrinkingdeformation of a heat-shrinkable sheet, the portion opposed to the flatwall of the square tube has large shrinkage as compared with the portionopposed to the ridge-line. As a result, the end of a shrunk label woundaround the bottle is wrinkled which deteriorates the external appearanceand style of the goods.

When the shoulder portion extension is not sufficient as compared withthe square tubular body, a large difference of extension is generatedbetween the ridge line of the shoulder and the flat wall portion,resulting in incorrect thermal deformation at the shoulder portion bythis non-uniform extension.

Among numerous characteristics inherent to the above PET bottle,transparency is extremely excellent and effective for increasingvisibility of the goods.

Thus, the PET bottle has excellent transparency. As compared with aglass bottle exhibiting the same excellent transparency however, the PETbottle is simply clear and does not exhibit any crystal effect due todeflection of transmitted light, so as to be poor in visual change.

One of the principle reasons why a crystal effect is low in the PETbottle having excellent transparency is because the PET bottle is abiaxially oriented blow molded good, so that its thickness is thin andtransmitted light cannot sufficiently be deflected.

It has therefore been considered to make the PET bottle thick to providea sufficient crystal effect. However, if the PET bottle is made thicker,expensive PET material is increased in the amount required for moldingone product, and, as a result, a unit price becomes high, biaxially blowmolding techniques become extremely difficult, and sufficienttransparency cannot be obtained without biaxially oriented deformation.

SUMMARY OF THE INVENTION

A primary object of the invention is to provide a container exhibitingthe function of a groove sidewall of a central circumferential grooveand a recess sidewall of a recessed portion as reinforcing rib wallpieces, and to create a self recoverable curved depressed deformation atthe time of deformation rather than a sharply bent depresseddeformation.

Another object of the invention is to prevent the appearance of reducedpressure deformation which would change the external appearance andshape of the bottle and to prevent deterioration of the externalappearance and style of the bottle by attaining reduced pressurecompensating deformation of a shaped panel wall for compensatingnegative pressure generated in the bottle by depressed deformation ofthe whole shaped panel wall.

A further object of the invention is to increase self configurationretaining capability of the shaped wall itself and to provide aninteresting external appearance.

An additional object of the invention is to remove or minimizeconspicuous corrugation at the upper edge of a shrunk label bypositioning such corrugation in the vicinity of the shoulder portion ofthe bottle, and to minimize non-uniformity of extension along thecircumferential direction at the shoulder portion.

Another object of the invention is to exhibit a satisfactory crystaleffect in the PET bottle without increasing the thickness of the PETbottle.

Other objects of the invention become clear from the description andaccompanying drawings.

According to a first aspect of the invention, it is possible to obtain abiaxially oriented blow-molded bottle-shaped container made of syntheticresin with the container comprising a rectangular tubular body providedwith a central circumferential groove substantially at a center of avertical length of the rectangular cylindrical body. The centralcircumferential groove has upper and lower sidewalls being inclined atan oblique angle within a range of 21°-28° with respect to a verticallongitudinal axis of the container.

Moreover, the oblique angle with respect to the bottle center axis ofthe groove sidewall is measured as an acute angle parallel to the bottlecentral axis rather than radially from the bottle central axis. So, theoblique angle of the upper groove sidewall and that of the lower groovesidewall are measured from opposite directions.

In the first aspect of the invention, the central circumferentialdepressed groove is provided at a substantially central portion of thebody, so that the wall portion for connecting the upper and lower groovesidewalls and the adjacent flat walls is curbed and projected into thebottle surface. Therefore, the groove sidewalls function to counteractpressure acting on the central circumferential groove portion as areinforcing rib wall piece, so as to prevent the body wall portion underpressure from simple depressed deformation. When strong pressure forceacts to generate a depressed deformation, the junction portion forconnecting the groove sidewalls and adjacent flat walls become aprojecting deformation for reversing the projection posture.

Even in the bottle viewed from the first aspect of the invention, thejunction portion for connecting the center peripheral groove and theadjacent flat walls becomes a projecting deformation in the same manneras the prior bottle. However, in the case of the present invention, theoblique angle of the groove sidewalls is small so that the wholejunction portion for connecting the groove sidewalls and the flat wallsis curved and deformed as a depression. Thus, the oblique angle of thegroove sidewalls and the flat walls is sufficiently reduced by thisdepressed deformation, and the central portion, which is depressed by apressing force, is curved outwardly and deformed before the depressedamount becomes large. In the case of an outwardly curved deformation ofthe junction portion between the groove sidewalls and the flat walls,reverse deformation is generated under the sufficiently reducedcondition of the oblique angle of the groove sidewall and the flat wall.This reverse deformation does not become a bent or sharp deformation butrather curved deformation within the range of elastic deformation of thewall. Thereby, positive self restoration to the original is attainedwhen the pressing force disappears.

That is, upper and lower groove sidewalls of the central circumferentialgroove are set at oblique angles for exhibiting the function ofreinforcing rib wall pieces as large as possible within the range ofgenerating no sharply bent reverse deformation. Setting of the obliqueangle of the groove sidewall is sought from many experimental examples,and according to the experimental examples, if the oblique angle of thegroove sidewall is set at more than about 29°, self configurationsustaining capability becomes large, the whole junction portion betweenthe groove sidewalls and the flat walls when applying pressure becomeshard to cause a rounded depressed deformation, and as a result,depressed deformation at the junction portion becomes a rapid reversebending and the self configuration sustaining capability cannot beobtained. On the other hand, if the oblique angle of the groovesidewalls is set at less than about 20°, the groove sidewalls cannotsufficiently function as a reinforcing rib wall piece and selfconfiguration sustaining capability is low, so that it is difficult tohandle the bottle by grasping by hand.

Moreover, a depressed sidewall of a recessed portion provided at thecentral portion of the flat walls which form the body acts in the samemanner as the groove sidewalls of the central circumferential groove.The bottom wall of such a recessed portion is a shaped panel wall forabsorbing reduced pressure deformation, which effectively functions toretain self configuration of the body. However, in the recess sidewalls,the recessed sidewall portion positioned near the centralcircumferential groove employs an elongated projected curved wallstructure, so that it is difficult to form a curved depression.Therefore, in the same manner as the groove sidewalls of the centralcircumferential groove, the oblique angle of the recess sidewall portionof the recessed portion in the flat walls positioned near the centralcircumferential groove is set at 28°-21°. Thus, it becomes easy togenerate a curved deformation from the groove sidewalls to the flatwalls and for the recess sidewall to function as a whole, so as toeffectively prevent generation of local sharp reverse deformation.

In the case of positioning the recess sidewall adjacent to the centralcircumferential groove, the length of the recess sidewall is shorterthan that of the groove sidewalls of the central circumferential grooveadjacent the flat walls. Therefore, rounded reverse deformation ismainly generated on the side of the groove sidewall, and the recesssidewall is roundly depressedly deformed without any difficulty inreversing the curved deformation of the groove sidewall.

The depth of the central circumferential groove can be made shallow byconnecting the upper and lower groove sidewalls of the centralcircumferential groove by means of a groove bottom wall. However, undercertain dimensional limitations, such as a certain groove width of thecentral circumferential groove, limitation of the oblique angles of thegroove sidewalls and the recess sidewall, results in a shallow depth ofthe central circumferential groove and the recessed portion. Thus thedepths of the central circumferential groove and the recessed portion,which form the largest depression in the body can be minimized, so thatthere is no large difference of extension between each portion of thebody, particularly the flat wall, so as to obtain good centrifugalmolding of the body and largely reduce generation of local deformationafter molding.

According to the second aspect of the invention, there is provided abiaxially oriented blow-molded bottle-shaped container made of syntheticresin, said container comprising a rectangular tubular body includingflat walls; each of the flat walls having a central recessed portionhaving a bottom wall comprising a shaped panel wall for taking updeformation due to reduced pressure in the container, and a shapedperipheral groove invertedly curved around the shaped panel wall; theshaped panel wall having ribs traversing the shaped panel wall inparallel to each other, a crest of each of ribs having a larger radiusof curvature than that of a root thereof; and opposite ends of the rootbeing shallow along a large radius of curvature.

Since the shaped panel wall comprises a number of transversal ribs, theshaped panel wall is liable to curve in the vertical direction buthardly curve in the lateral direction by functioning as a reinforcingrib. Moreover, the shaped peripheral groove molded around the shapedpanel wall has an inwardly curved wall structure, so that it is easilydeformed in the curved direction, that is, the vertical direction withrespect to the flat wall surface.

Therefore, when negative pressure is generated in the bottle, the shapedpanel wall is largely curved along the vertical direction. Also, theshaped central circumferential groove is curved which depresses anddisplaces as the whole within the bottle, so as to take up the reducedpressure with sufficient volume.

As mentioned above, the shaped panel wall can be deformed with a largecurve in the vertical direction and also depressed or displaced as thewhole in order to take up the reduced pressure generated in thecontainer, so that the deformation due to the reduced pressure does notaffect the external appearance.

The shaped panel wall has a number of ribs extending transversely. Theseribs serve as reinforcing ribs and have a sufficient strength to supporturging pressure applied by finger tips and to generate an appropriatefriction resistance force between the bottle and finger tips when thebottle is grasped by the hand.

Each rib comprises a crest and root portion and these portions areformed by the curved wall structure, so that their moldability in blowmolding is excellent. Each opposite end of the root portion is madegradually shallow along a curve having a large radius of curvature sothat the corner portion between the flat walls is improved inmoldability.

The ribs thus forming the shaped panel wall provide a number of smallconcavities and convexities on the surface of the shaped panel wall.Therefore, the shaped panel wall has substantially different wallthickness in any direction owing to the many ribs. Consequently, whenthe bottle is made of a clear synthetic resin having high transparencysuch as polyethylene terephthalate, an optical crystal sense occurs inthe external appearance of the shaped panel wall by the large variationof wall thickness.

Moreover, when the height of the crest portion is as high as more thanthree times the radius of curvature of the root portion, the degree ofthe concave and convex shapes of the shaped panel wall can be made deep.As a result, the self configuration sustaining capability in thetransverse direction of the shaped panel wall is improved, and thevisible crystal sense is enhanced.

According to the third aspect of the present invention, there isprovided a biaxially oriented blow-molded bottle-shaped container madeof synthetic resin, the container comprising a rectangular tubular bodyhaving an upper end which is a regular polygon having twice as manycorners as corners or corner panels on a main portion of the body, and ashoulder having a lower end portion connected to the upper end of thebody; and the lower end portion of the shoulder being in the form of aregular polygonal truncated pyramid shape having twice as many cornersas corners of the main portion of the body.

A shrunk label is generally applied to the bottle from the upper halfportion to the lower end portion of the shoulder. Therefore, the upperedge of the shrunk label applied to the bottle is located at the lowerend portion of the shoulder and the opposed lower edge is located in thecentral circumferential groove.

Thus, the shrunk label is applied around the bottle in such a mannerthat the upper edge is wound around the reduced lower end portion of theshoulder and the lower edge is also wound around the reduced portion inthe central circumferential groove. Therefore, both the upper and loweredges are located in corresponding upper and lower portions of reduceddiameters, respectively. Thus, the shrunk label is prevented fromdrawing away from the bottle and is strongly and stably secured to thebottle.

The lower end portion of the shoulder where the upper edge portion ofthe shrunk label is wound has a regular polygonal shape and twice asmany corners as corner panels of the main portion of the body.Furthermore, the lower end portion has a smaller diameter than that ofthe main portion of the body. Therefore, the upper edge portion of theshrunk label which is wound around the lower end portion of the shoulderis under a condition that a difference of shrinkage between a portionfacing the ridge-line of the lower end portion of the shoulder and aportion facing the flat wall is small. Further, the shrinkage of theportion facing the lower end portion is uniform, and any displacementresulting from the shrinkage of the shrunk label in the verticaldirection is prevented by the upper end portion of the body which hasthe larger diameter. Accordingly, in the upper edge portion of theshrunk label wound around the lower end portion of the shoulder, largewrinkles do not occur.

On the other hand, the central portion of the body where the lower endof the shrunk label is wound has a rectangular tubular shape. Therefore,the lower edge portion of the shrunk label has different shrinkagebetween a portion facing the ridge-line of the central portion of thebody and a portion facing the flat wall. As a result, the lower edgeportion of the shrunk label is wrinkled. However, in the present case,the central circumferential groove is provided at the central portion ofthe body and the lower edge of the shrunk label is located in thecentral circumferential groove. Accordingly, a portion of the shrunklabel at just above the lower edge located in the centralcircumferential groove is initially applied to the surface of the bodyand then prevents any displacement of the lower edge portion resultingfrom the shrinkage of the shrunk label in the vertical direction.Consequently, large wrinkles also do not occur at the lower edge of theshrunk label.

Furthermore, since the lower end portion of the shoulder is molded inthe shape of regular polygon, average elongation of each combination ofthe flat wall and ridge-line portion at the lower end portion of theshoulder is the same. Since the lower end portion of the shoulder hastwice as many corners as corner panels of the main portion of the body,the difference of elongation between the flat wall portion and theridge-line portion is sufficiently small. Accordingly, the lower endportion of the shoulder can be uniformly molded with substantially thesame elongation. Since the lower end portion of the shoulder isuniformly elongated in the circumferential direction during blowmolding, even if thermal deformation occurs in the shoulder portion dueto insufficient elongation, the thermal deformation uniformly occurs inthe circumferential direction and therefore irregular deformation doesnot appear in the external appearance of the shoulder portion due to thethermal deformation.

According to the fourth aspect of the present invention, there isprovided a biaxially oriented blow-molded bottle-shaped container madeof synthetic resin having a high clarity, the said container includingtwo sets of wall surface portions of first wall surfaces and second wallsurfaces which are formed at the shoulder and the bottom, respectively,and are connected through curved lines to each other. A connecting edgeof the first wall surface connected to the second wall surface isslightly extended toward the second wall surface. The extended edge ofthe first wall surface is connected to a connecting edge of the secondwall surface through a ridge-line portion which is inwardly curved witha small radius of curvature.

The first wall surface and the second wall surface which are connectedat the ridge-line wall portion, are not specified in respect toindividual wall structure and a combination of mutual wall structures,but at least one of the wall surfaces is preferably a flat wall surfacestructure. Particularly, the first wall surface may be a flat wallstructure and the second wall surface may be a curved wall structure.

Since the connecting edge of the first wall surface is slightly extendedand this extended edge of the first wall surface is connected to theconnecting edge of the second wall surface at the ridge-line wallportion, the curved line, i.e., ridge-line portion formed between boththe wall surfaces, forms a protruded ridge-line which protrudes in thedirection of the extended connecting edge of the first wall surface.

The protruded ridge-line portion is more sharply protruding than that ofthe usual ridge-line portion to thereby enhance the difference of therefraction direction of the transmitted light through each of the wallsurfaces which have different angles of inclination starting from theprotruded ridge-line.

Furthermore, the ridge-line wall portion of the protruded ridge-line isinward with a small radius of curvature to locate it in an attitudesubstantially standing to the transmitted light passing in the directionof thickness of both of the wall surfaces. Thereby, the ridge-line wallportion provides a locally thickened wall portion for the transmittedlight by the ridge-line wall portion. It will be seen from the abovethat since the ridge-line wall portion provides a locally thickened wallportion for the transmitted light, the transmitted light passing throughthe ridge-line wall portion is subjected to greater refraction than thatof transmitted light passing through the adjacent other portion, i.e.,both the wall surface portions.

If one of the adjacent wall surface portions is the flat wall structure,particularly if the first wall surface is the flat wall structure andthe second wall surface is the curved wall structure, the amount ofextension of the protruding ridge-line can be increased within a narrowrange to thereby provide a relatively strong refracting action for thetransmitted light. Further, the radius of curvature of the inward curveof the ridge-line wall portion can be slightly increased, therebycausing the bottle to be easily molded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view illustrating a bottle according to the presentinvention;

FIG. 2 is a cross sectional view taken on line II--II of FIG. 1;

FIG. 3 is an enlarged vertical sectional view of a portion enclosed by acircle in FIG. 1;

FIG. 4 is a cross sectional view of a body of the bottle shown in FIG.1;

FIG. 5 is a partial enlarged cross sectional view of a flat wall of thebottle shown in FIG. 1;

FIG. 6 is a partial enlarged vertical sectional view illustrating a ribon a modified panel wall;

FIG. 7 is a plan view of the bottle shown in FIG. 1;

FIG. 8 is a cross sectional view taken on line VIII--VIII of FIG. 1;

FIG. 9 is an enlarged front view of the bottom portion of the bottleshown in FIG. 1;

FIG. 10 is a bottom plan view of the bottle shown in FIG. 1;

FIG. 11 is a sectional view of a wall taken on line XI--XI of FIG. 9;and

FIG. 12 is an enlarged detail of a protruded ridge-line portion shown inthe sectional view of FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, an embodiment of a bottle according to the presentinvention will be explained with reference to the drawings.

Referring to an embodiment shown in the drawings, a bottle 1 has alongitudinal axis A--A and a body 2 formed in the form of a square tube.The body has four ridged-line walls 13 at corners thereof, respectively,each of which is formed by an arched wall as shown in FIG. 2. The bodyhas also a generally central circumferential groove 3 which is formed ata central position slightly higher than half of the whole height todivide each of four flat walls 6 into upper and lower portions 2a and2b, respectively. The body further has a bottom 2c having a centralcurved recess retracted inwardly into the bottle 1 and an upper endportion 2d having a diameter which is gradually reduced from a shoulder11 having a semispherical shape and has an opening 12 at the upper endthereof.

Each of the upper and lower portions 2a and 2b of the flat wall 6divided by the circumferential groove 3 has a recessed portion 7a and 7bformed at a central portion thereof. Each recessed portion 7a and 7b hasa shaped bottom panel wall 8 at the central portion thereof and adeformed sidewall 9 at the peripheral portion thereof.

A portion of the sidewall 9b of the recessed portion 7b adjacent to thecircumferential groove 3 that is the upper portion 92 of the sidewall 9bin the lower recessed portion 7b and the lower portion 91 of the sidewall 9a in the upper recessed portion 7a extend approximately straightalong the circumferential groove 3 so that the portions of the flat wall6 between the circumferential groove 3 and the recessed portions 7a and7b can be easily bent as a whole.

The circumferential groove 3 as shown in FIG. 1 has a flat bottom wall 5and corners having a large radius of curvature in the cross sectionthereof as shown in FIG. 2 so that the circumferential groove 3 hassmaller depth at a portion opposed to the flat wall 6 than that at aportion opposed to the ridge-line wall 13. As a result, the portionopposed to the ridge-line wall 13 of the circumferential groove 3 ishardly deformed, while the portion opposed to the flat wall 6 is easilybent or depressed. Therefore, when portions of the circumferentialgroove 3 and the flat wall 6 are bent or deformed by depressing, theridge-line walls 13 act as strong supporting portions so that thedeformation of the groove and the flat wall is effected in a stablemode.

FIG. 3 illustrates an embodiment of a wall structure near thecircumferential groove 3 in vertical section. A bottle 1 including sucha wall structure has an internal space of 1.5 liter and is shaped suchthat the volume of the lower body portion 7b is larger than that of theupper body portion 7a positioned above the circumferential groove 3. Insuch a wall structure, since the lower side wall 4b of thecircumferential groove 3 is mainly subjected to a depressing force bygrasping when the bottle is handled, the lower side wall 4b of thecircumferential groove 3 is set at a maximum angle α of inclination of27°, while the upper side wall 4a of the circumferential groove 3 is setat an angle α of inclination of 24° and the angle α of inclination ofthe sidewall 91, 92 of the recessed portions 7a and 7b, respectively,opposed to the circumferential groove 3 is set at an angle α of 21°.

The angle of inclination of the groove sidewalls 4a and 4b and therecess sidewall 91, 92 and their combination may be selectively set in arange of 21°-27°, but since the purpose of providing the circumferentialgroove 3 is to enhance the angle of inclination of the lower groove sidewall 4b which is subjected to the depression force upon handling of thebottle 1 may be set at the maximum to enhance the self configurationsustaining capability of the body 2 owing to the circumferential groove3.

It has been found from results of many experiments that when all of thegroove sidewalls 4a and 4b and the recess sidewalls 91, 92 are set at anangle of inclination of 27°, a higher self configuration sustainingcapability than that of the embodiment shown in FIG. 3 is obtainable,but a mode of a self returning operation from a sharp inward deformationis not smooth and particularly such a tendency is remarkably enhanced asthe angle of inclination of the lower sidewall 4b of the circumferentialgroove 3 is set at a larger angle. It is been proven to be advantageousfrom the results of experiments to set the angle of inclination of therecess sidewalls 9 small.

According to the second aspect of the present invention, a number ofribs 21 extending parallel to each other are transversely formed on theshaped panel wall 8 as shown in FIG. 6. These ribs 21 define crests 22and roots 23, and the radius of curvature R of the crest 22 is set tofour times the radius of curvature r of the root 23 to thereby enhancemoldability of each of ribs 21.

The ridge-line of the crest of each of ribs 21 is set to the same heightas that of the inner peripheral edge of the deformed peripheral groove 9of each recessed portion 7a and 7b so as to connect the opposite ends ofthe rib to the inner peripheral edges of the deformed peripheral groove9 directly, respectively. The opposite ends of the root 23 becomegradually shallow along a curve having a large radius of curvature toconnect to the inner peripheral edges of the deformed peripheral groove9, respectively. Thus, the opposite ends 23a and 23b of the root 23 areformed gradually shallow along a curve of a large radius of curvature,so that it is capable of enhancing the moldability of the ridge-linewall 13 which is continuously elongated after the flat wall 6 has beendeformed during the blow molding of the bottle.

According to the third aspect of the present invention, the upper endportion of the bottle body shown in FIG. 7 is preferably shaped as aregular polygon having two times as many corner walls as that of themain portion of the body by forming the ridge-line walls at the cornersof the upper end portion of the body as arched shaped walls 34 tothereby provide a regular polygonal tubular shape by the flat walls andthe ridge-line walls and then gradually reducing the diameter of theupper end portion of the body to decrease the width of the flat wallsand increase the width of the ridge-line walls. As shown in FIG. 7, thisembodiment has four side walls 6, with corner walls 13, and eight sidewalls 34 forming the upper end portion. In the embodiment shown in thedrawings, the diameter of the upper end portion of the body 2 isgradually reduced to decrease the width of the flat walls 6 and increasethe width of the ridge-line walls 7 to thereby shape the upper endportion of the body as a regular octagon. It is desirable in view ofexternal appearance and molding that the body is molded in a squaretubular shape.

The lower end portion 31 of the shoulder 11 continued to the upper endof the regular octagonal portion of the body 2 has a shape of a lowregular octagonal truncated pyramid extended directly from the upper endof the body 2. The upper end of the lower end portion 31 is continued toa main portion 33 in the form of a semispherical shell as a remainder ofthe shoulder 11 through a narrow stage portion 32. The main portion 33is provided with an opening 12 at the upper end thereof. The lower endportion of the semi-spherical main portion 33 has inclined flat wallportions 34 continued to the flat walls in the lower end portion 31,respectively, and a scalloped ridge-line 35 formed as a boundary betweenthe inclined flat wall portions 34 and the semi-spherical surface 33.

A shrunk label printed with a display such as a commercial name,contents and the like is applied to the upper half portion 2a defined bythe circumferential groove 3 of the body 2 with the lower edge of theshrunk label being positioned in the circumferential groove 3 and theupper edge of the label being positioned on the stage portion 32 of theshoulder 11. By positioning the lower edge of the shrunk label in thecircumferential groove 3, i.e., on the upper groove surface 4a of thecircumferential groove 3, the shrunk label is hardly viewed by theexternal appearance of the bottle. Therefore for example, even if thelower edge of the shrunk label has been slightly wrinkled, the externalappearance of the bottle will not be affected by the wrinkle. Similarly,since the upper edge of the shrunk label is located on the stage portion32, which forms a flat surface along the radial direction, the upperedge of the shrunk label is hardly wrinkled. Moreover, since both theupper and lower edges of the label are located in areas which aresharply reduced in diameter, the shrunk label is very strongly andstably attached to the bottle 1.

A wall structure arranged according to the fourth aspect of the presentinvention is applied to the shoulder 11 and the bottom portion 10 of thebottle 1. In the case of the shoulder 11 shown in FIG. 7, the mainportion 33 of the shoulder constitutes the second wall surface and theflat wall portion 34 constitutes the first wall surface. While, in thecase of the bottom 10, as shown in FIGS. 9 and 10, the peripheral wallof the base portion 10 which is the tapered cylindrical wall portionextending upwardly from the bottom comprises the second wall surface 42and a flat wall surface 41 which is formed by obliquely cutting theupper half portion of the second wall surface 42 continued to the flatwall portion 6 of the body 2.

An embodiment of the wall structure arranged according to the presentinvention is illustrated in a sectional view of FIG. 11 which is asection taken on line XI--XI in FIG. 9 illustrating the embodiment ofthe bottom portion 10. A portion of a protruded ridge-line 43 shown inFIG. 11 is illustrated in FIG. 12 in enlarged scale.

By comparing the portion of the protruded ridge-line 43 of the wallstructure according to the present invention shown by a solid line witha prior art wall construction of a ridge-line wall portion shown by adotted chain line, it is shown that a protruding amount of the protrudedridge-line 43 is greatly larger than that of the prior art ridge-linestructure and that the ridge-line wall portion 44 constituting theprotruding ridge-line 43 is bent over with a small radius of curvatureto locate a portion of the ridge-line wall portion as a standing ribwall.

According to the above arrangement of the present invention, thefollowing effects are obtained.

By controlling the angle of inclination of the groove sidewalls 4a and4b, any bent and/or depressed deformations which could not be restoredcan be perfectly prevented from occurring in the junction between thegroove sidewalls 4a and 4b and the flat wall portion 6, as a resultthere is no inconvenience of bent and/or depressed permanentdeformations.

Since any bent and/or depressed deformation occurring in the junctionbetween the groove sidewalls 4a and 4b and the flat wall portion 6 is anelastic deformation in all of the range of its deformation, when thebottle is grasped by the hand and consequently bent and/or depressed bya depressing force, the finger tips of the hand applying the depressingforce is always counteracted by a rebound so that a stable graspingoperation is achieved even if the bent and/or depressed deformationoccurs.

By controlling the angle of inclination of the groove sidewalls 4a and4b and the recess sidewalls 9 to a relatively small amount, the depth ofthe circumferential groove 3 and the recessed portions 9 can be madeshallow and the degree of concavity and convexity in the body 2 can bemade small. Therefore, the amount of elongation in the flat wall portion6 can be uniformized to provide a bottle having a good moldability andless deformation.

The shaped panel walls 8 can be deformed for taking up the negativepressure by a large bent deformation of the whole shaped panel wall 8and an inward depressed deformation of the whole shaped panel wall 8.Therefore, such a negative pressure compensating deformation in therecessed portions 9 is not observed in the external appearance of thebottle to thereby prevent degradation of the external appearance causedby the deformation of compensating for negative pressure and reserve theexcellent external appearance of the bottle.

The ribs 21 serve as reinforcing ribs to enhance the self configurationsustaining capability in the transverse direction of the modified panelwall portion 8. Accordingly, when the bottle is grasped by hand, theshaped panel wall 8 which is pressure contacted with the finger tips ishardly depressed by the pressure of the finger tips and supports theurging pressure. Therefore, the bottle can be stably grasped by hand andsmoothly and stably handled as the whole.

The modified panel wall 8 comprises a number of ribs 21 to form a wallstructure having a concave and convex shape with undulations providing astrong optical action to transmitted light. Therefore, the body 2 of thebottle 1 can provide an appearance having a crystal-like decorationeffect by optical action, and the external appearance of the bottle canbe satisfactorily improved.

When the shrunk label is attached around the body 2 of the bottle, theupper edge of the shrunk label is located on the lower end portion 31 ofthe shoulder 11 of a regular polygonal tubular shape having twice asmany corner walls as in the body, shown as walls 13 and 34. As a result,the upper edge of the shrunk label is hardly wrinkled. Therefore, theexternal appearance of the bottle is not negatively impacted by wrinklesin the edge of the shrunk label.

The upper edge of the shrunk label is located on the lower end portionof the shoulder 11 having a reduced diameter and the lower edge islocated in the circumferential groove 3 having a reduced diameter.Therefore, the shrunk label can be strongly and stably attached to thebody with simple shrinkage.

Since the lower end portion 31 of the shoulder is formed in the shape ofa regular polygonal truncated pyramid, the elongation along thecircumferential direction is substantially uniformly achieved.Therefore, even if the shoulder 11 is thermally deformed, this thermaldeformation occurs uniformly over the shoulder 11, and there is nostrain causing degradation of the external appearance of the shoulder.

In the bottom 10 of the bottle 1, the ridge-line 43 at the boundarybetween the flat wall surface 41 and the second wall surface 42 can begreatly protruded. Then, the corner formed by thus protruded ridge-line43 can be sharply observed. Therefore, any difference of degree ofrefraction of transmitted light between both the wall surface portionsis emphasized and then the crystal effect is enhanced.

A part of the ridge-line wall portion 44 where the ridge-line is curvedover can be located in the form of a ribbed wall piece standing withrespect to both the wall surface portions to provide a thicker portionto the transmitted light and thereby sufficiently refracting thetransmitted light. Consequently,, the ridge-line wall portion can give amore remarkable crystal effect.

The protruded ridge-line 43 slightly extends the connecting edge of theflat wall surface 41. The thus extended connecting edge is onlyconnected to the connecting edge of the second wall surface 42 at thecurved over ridge-line wall portion 44. Accordingly, the bottle 1 can beeasily and accurately molded in the conventional molding operationindependent of whether a new or existing molding die is used.

What is claimed is:
 1. A biaxially oriented blow-molded bottle-shapedcontainer made of synthetic resin comprising:a body having a verticallongitudinal axis provided with a circumferential groove substantiallyat a central portion of a vertical length of the body, wherein thecircumferential groove has upper and lower sidewalls inclined at anoblique angle within a range of 21°-28° with respect to the verticallongitudinal axis of the container.
 2. The container according to claim1, wherein the circumferential groove has a flat groove bottom walldisposed between the sidewalls.
 3. The container according to claim 2,wherein the groove sidewalls are inwardly inclined toward the groovebottom wall at an angle of about 27° with respect to the verticallongitudinal axis.
 4. The container according to claim 1, wherein thebody has a plurality of flat walls divided into upper and lower sides bythe circumferential groove, each of the flat walls having a centralrecessed portion with a bottom wall comprising a shaped panel wallformed to compensate for deformation due to reduced pressure in thecontainer andthe recessed portion has a recessed sidewall adjacent theshaped panel wall at a side near the groove sidewalls inclined at anoblique angle within a range of 21°-28° with respect to the verticallongitudinal axis of the container.
 5. The container according to claim4, wherein the recessed sidewall of each recessed portion extendsannularly around the respective recessed portion.
 6. The containeraccording to claim 4, wherein the recessed sidewall of each recessedportion is inclined at about 21° with respect to the verticallongitudinal axis of the container.
 7. A biaxially oriented blow-moldedbottle-shaped container made of synthetic resin, comprising:a bodyincluding flat walls, each of the flat walls having a central recessedportion having a bottom wall comprising a shaped panel wall forcompensating deformation due to reduced pressure in the container, and ashaped peripheral groove curved around the shaped panel wall, whereinthe shaped panel wall has ribs each with a curved crest and a curvedroot traversing the shaped panel wall in parallel to each other, thecrest of each of the ribs having larger radius of curvature than that ofthe root.
 8. The container according to claim 7, wherein the radius ofcurvature of the crest of each of the ribs is at least three times aslong as the radius of curvature of the root.
 9. The container accordingto claim 7, wherein each rib has opposed ends and extends across therespective shaped panel wall, one end adjacent a portion of the shapedperipheral groove and the other end adjacent an opposed portion of theshaped peripheral groove, the opposite ends of the root being curvedinwardly and joining the shaped peripheral groove along a large radiusof curvature.
 10. The container according to claim 7, wherein the shapedperipheral groove is concave with respect to the flat walls.
 11. Thecontainer according to claim 10, wherein each shaped peripheral grooveis inclined from the flat wall at an angle in the range of 21°-28°measured from a vertical axis of the container.
 12. The containeraccording to claim 7, further comprising a generally centralcircumferential groove having sidewalls inwardly inclined at an anglefrom the flat walls in the range of 21°-28° measured from a verticalaxis of the container.
 13. A biaxially oriented blow-moldedbottle-shaped container made of synthetic resin, comprising:arectangular tubular body having a main portion with four corner wallsand an upper end which is a regular polygon having eight corner wallsand a shoulder having a lower end portion connected to the upper end ofthe body, the lower end portion of the shoulder being in the form of aregular polygonal truncated pyramid shape having eight corner walls. 14.The container claimed in claim 13, wherein the corner walls of the upperend portion of the body comprise four substantially flat ridge-linewalls and four intermediate flat walls each disposed between a pair ofridge-line walls to form a regular polygonal tubular shape, whereintheupper end portion is gradually reduced in diameter to decrease a widthof each of the intermediate flat walls and to increase a width of eachof the ridge-line [wall]walls to form the regular polygon.
 15. Thecontainer according to claim 13, wherein the shoulder has an upper endportion which is a semispherical shell portion and the lower end portionof the shoulder is connected to the semispherical shell portion of theshoulder through a narrow stage portion, and a portion of thesemispherical shell portion opposed to each flat wall adjacent the lowerend portion of the shoulder has inclined flat wall portions.
 16. Thecontainer according to claim 13, wherein the body has a circumferentialgroove which is depressed in a substantially central portion of thebody.
 17. The container according to claim 13, wherein the body has asquare tubular shape.
 18. The container according to claim 13, whereinthe body has a plurality of shallow recessed portions.
 19. A biaxiallyoriented blow-molded bottle-shaped container made of synthetic resinhaving a high clarity, comprising a body, a shoulder and a bottom andincluding two sets of first wall surface portions and second wallsurface portions, each set formed at the shoulder and the bottom,respectively, and each first wall surface portion connected to a secondwall surface portion through a curved edge, whereinthe curved connectingedge of each first wall surface portion connected to each second wallsurface portion extends toward the second wall surface portion andincludes a ridge-line wall portion which is inwardly curved with a smallradius of curvature.
 20. The container according to claim 14, whereinthe first wall surface portion is a flat wall structure, and the secondwall surface portion is a curved wall structure.
 21. The containeraccording to claim 1, wherein the body has a plurality of flat walls andeach first wall surface portion is coupled to a flat wall and extendstherefrom.
 22. The container according to claim 21, wherein each flatwall has a central recessed portion therein.
 23. A container formed ofbiaxially oriented blow-molded synthetic resin and having a verticalaxis, comprising:a tubular body having flat sides; a plurality ofcorners connected between the flat sides; a shoulder connected to anupper part of the body; and a bottom connected to a lower part of thebody, wherein the body has a circumferential groove therein withinclined sides and a groove bottom, the groove sides being inclined atan angle in the range of 21°-28° measured from the vertical axis, andhas a plurality of recessed portions with inclined sides and a texturedpanel bottom, the recessed portion sides being inclined at an angle inthe range of 21°-28° measured from the vertical axis, wherein theshoulder has a plurality of flat wall portions, each flat wall portioncorresponding to one of one of the flat sides and one of the corners ofthe body, and wherein the bottom connected to the lower part of the bodyhas first and second surfaces, each first surface extending from one ofthe flat sides of the body and each second surface being connected to afirst surface by a ridge-line.